DESCRIPTION (provided by investigator): The overall goal of this project is to develop therapies against Yersinia pestis, the causative agent of plague and one of the most dangerous potential bioweapons. We recently developed a general method to grow previously "unculturable" microorganisms (Kaeberlein, T., Lewis, K., and Epstein, S.S. (2002). Science 296:1127-1129), and this proprietary technology will serve as a platform for antibiotic discovery. Most antibiotics currently in use are derived from cultivable microorganisms that make up <1% of all species. Discovery of novel compounds essentially ceased in the 70s due to overmining of cultivable species. Unculturable microorganisms are the richest source of biodiversity on this planet, and we will access this essentially unlimited resource to discover antibiotics acting against Y. pestis. The goal of Phase I is to establish screens for antimicrobial compounds from unculturable microorganisms, and obtain proof-of principle for this technology by identifying compounds with chemical novelty. This will enable large-scale screening and validation in Phase II that will produce lead compounds, ultimately resulting in a new antibiotic product. The Specific Aims are: 1. Tools to obtain and screen unculturable microorganisms. The diffusion chamber approach will be used to isolate and grow unculturable microorganisms. (Milestone: we will obtain 1,000 novel isolates by this method). Additional novel methods for rapid isolation, screening and scale up will be developed: Helper organisms will be identified that enable growth of unculturable microorganisms on synthetic media in vitro. Domestication of unculturable microorganisms will result in variant growing on regular synthetic media. (Milestone: using these methods, we will achieve a rate of screening for antibiotic producers of >105 isolates/year). 2. Extract screening and preliminary validation. (Milestone: screen 4,000 extracts). 3. Dereplication and structure determination. (Milestone: identify 5 chemically novel compounds).